Conventionally, there are known technologies to mold a resin optical system (a lens or a compound lens) and its holder (casing), a cover (lid) within the same mold and to assembly those members (for example, Patent Literature 1).
According to the technology of Patent Literature 1, an optical system (lenses 35, 37), a holder (cylindrical frame 33) and cover (lid 38) are simultaneously molded, and the optical system is inserted into the holder, which has been molded, with the movement of movable mold (4) under the condition that the optical system and the cover are left on fixed mold (3), then the cover is bonded to the holder (paragraphs 0026-0032).